Radio frequency shielded container for electronic devices



R. 'A. RAWLEY -Oct. 16, 1956 RADIO FREQUENCY SHIELDED CONTAINER FORELECTRONIC DEVICES Filed March 31, 1954 FIG-.3

INVENTOR. A. RAWLEY RALPH BY d;

ATTORNEY United States Patent RADIO FREQUENCY SHIELDED CONTAINER FORELECTRONIC DEVICES Ralph A. Rawley, Wenham, Mass., assignor to BomacLaboratories Inc., Beverly, Mass., a corporation of MassachusettsApplication March 31, 1954, Serial No. 420,013 2 Claims. (Cl. 229--3.5D

The present invention relates to improvements in tubular containers and,more particularly, to an improved container for electronic devices thatare extremely sensitive to radio frequency energy.

Devices of the type referred to in the art as crystal or dioderectifiers generally employ a semi-conductor material such as germaniumor silicon which have very sensitive rectification properties. Suchdevices may be found in radar receiving apparatus to detect low powerreflected radio frequency signals. Due to the inherent sensitivity ofthese devices, they may be damaged by exposure to radio frequency energyin excess of the limit of the device. This phenomenon is referred to asburn-out. It is, therefore, necessary to provide such devices with someform of radio frequency shielding during shipment or in storage.

The desired protection has been afforded in the electronics industry bymeans of a lead capsule or a nonmagnetic electrically conductivematerial completely enclosing the device with further standard paperboard outer packaging. Such protection requires not only additionalexpense in the cost of materials, but increases assembly labor costssince the operator must be certain that the device is completelyshielded. Further, if the packaged article must be removed for testingduring storage, it is difiicult to re-package in the original containerbecause the metallic material is readily deformable and subject tocracking, splitting or tearing after several foldings. it is sometimesmore convenient to employ a new container, rather than have the articleinadequately protected.

1 t is an object of the present invention to provide means packagingsensitive electronic devices with radio fre quency radiation protectionincorporated in a unitary structure.

A further object is to provide a simple and inexpensive container forpackaging semi-conductor rectifiers which will adequately shield saidarticles from radio frequency energy during transit and storage.

A feature of the invention resides in the construction of a tubularcontainer comprising two spirally wound inner layers of a paper backedmetallic foil material with the foil in face to face relationship. Anouter layer of a lrraft or other similar paper board is spirally woundaround the foil layers to complete the tube. The embodiment of myinvention provides within itself safe protection from exposure to radiofrequency energy. Because of the simplicity of construction the shieldedtube be manufactured on standard paper tube machinery.

Other objects, features and advantages will be more readily appreciatedafter consideration of the following detailed specification andaccompanying drawings, in which:

Figure l is a perspective view of the illustrative embodiment with thecomponents partially broken away to disclose underlying structure;

Figure 2 is an end view in detail of the complete container;

Figure 3 is a detailed vertical cross sectional view of the embodimentwith the exposed packaged article in perspective; and

Figure 4 is a detailed vertical cross sectional view of an alternativeembodiment.

As shown in Figure l the illustrative embodiment 1 comprises an innertubular sleeve formed by a spirally wound layer of a thin paper backedmetallic foil material 2 having foil face 3 extending outwardly.Spirally wound on this layer is a similar material 4 with the foil 5 inface to face relationship with underlying foil layer 3. This layer iswound in such a manner that the butt joint 6 of the underlying layer isoverlapped. Any suitable adhesive bonds the two paper backed foil layerstogether. In the illustrative embodiment an aluminum foil materialhaving a foil thickness of approximately one thousandth of an inch wasemployed. An outer sleeve of a kraft or similar fibrous material 7having a thickness approximately equal to that of the inner two layersleeve is spirally and adhesively wound on said inner sleeve to completethe container. This layer may also be formed so as to overlap the buttjoint 8 of layer 4.

As shown in Figure 3 the sensitive electronic device 9 of tubularconstruction when supported in my improved container will be safelyprotected from radio frequency energy even with the ends of saidcontainer open. If desired, the container 1 may be modified as shown inFigure 4 to provide a complete enclosure. A disc shaped end member 10having a foil face disposed inwardly may be provided at one end with anouter body member 11 friction-fitted over the tubular container 1. Asimilar disc member 12 is disposed at the other end followed by afriction-fitted cap 13 having a foil lining 14. Said cap rests againstouter body member 11 as at 15.

Various other modifications will occur to those skilled in the art. Itis, therefore, my intention to cover in the appended claims suchmodifications or variations as fall within the spirit and scope of theinvention.

What is claimed is:

1. Radio frequency shielded tubular container for elec tronic devicescomprising a spirally wound inner layer of a thin metallic foil materialhaving a fibrous material backing with said foil material extendingoutwardly, the adjacent edges of said inner layer forming a butt joint,an intermediate layer of a similar material spirally wound on andadhesively secured to said inner layer with said foil material in faceto face relationship and the spiral windings of said intermediate layeroverlapping the butt joints of said inner layer, and an outer layer of afibrous material spirally wound on and adhesively secured to the fibrousmaterial of said intermediate foil layer.

2. A radio frequency shielded tubular container for a semi-conductorcrystal unit comprising an inner sleeve having a plurality ofsuper-imposed spirally wound layers of a metallic foil material having afibrous material backing with said foil material positioned in face toface relationship, the inner layer of said inner sleeve having adjacentedges forming a butt joint, the outer layer of said inner sleeveoverlapping the butt joint of adjacent edges of the underlying innerlayer and an outer sleeve of a fibrous material surrounding said innersleeve.

References Cited in the tile of this patent UNITED STATES PATENTS732,862 Jones July 7, 1903 1,983,520 Charch et al Dec. 11, 19342,039,372 Wickrnann May 5, 1936 2,247,197 Graves June 24, 1941 2,355,584Douglas Aug. 8, 1944 2,484,608 Cheyney et al. Oct. 11, 1949 2,555,380Stuart et al. June 5, 1951

